The development of a new computerized interferometer is described which allows non-contact measurement of surface topography with vertical resolution better than 0.5 mm over a 0.5 mm by 0.3 mm sample area. A detailed (40000 vertical measurement) three-dimensional image (phase map) is graphically displayed along with a video contrast micrograph of the same sample area. Post-processing of the data yields, average deviation, r.m.s. deviation, peak-to-valley, and asperity volumes are reported on all or user selected subsets of the data. During this post-processing, the region currently being measured in the phase map is highlighted in the video contrast micrograph allowing positive correlation of contrast micrograph features with measurements in the phase map. Applications to video tape, rigid disk, substrate, and read-write head measurements are discussed.